The main magnitude that we have studied to characterize the
dynamical behavior is the average escape time of the trajectories,
\(T\) . Because the system is 4-dimensional and we have to deal with
3 free coordinates, there exist many methods to launch trajectories
in phase space in order to obtain \(T\) . Some researchers fix the
physical coordinates as \((x,y)=(0,0)\)  and then vary the angle
of the launching. Other authors prefer to fix the angle and vary the
physical coordinates over a line segment in the physical space. In
order to consider a more general range of initial conditions in phase space, here we have used the tangential shooting method
[1]}. Using this method, the velocity vector is defined
in such a way that is tangent to the circle centered at the origin
and passing through the point \((x_0,y_0)\) . This consideration
implies that when we vary \((x_0,y_0)\)  we are also varying
\((p_0,q_0)\) , so we are exploring initial conditions in all the phase
space. To choose a suitable method to define the initial conditions
is important, especially in the mixed-phase-space-regime, because it is
possible to miss some parts of the dynamical behavior (trapped
trajectories for example) by choosing specific sets of initial
conditions.
